One of the great frontiers of modern neuroscience is the ongoing effort to understand how memory is processed in the brain. While the last decade has witnessed tremendous advances in our understanding of the synaptic and molecular basis of neuronal plasticity, much less is known about how the diverse forms of plasticity revealed in these studies directly relate to bone fide learning and memory. The main focus of this research project is to use the marine mollusc Aplysia to provide direct links between synaptic and molecular plasticity expressed on a cellular level, and specific phases of memory for sensitization expressed behaviorally. Towards that end, there are three specific aims to the overall project: (1) A BEHAVIORAL ANALYSIS will be aimed at elucidating the behavioral features of different phases of memory for sensitization (short-term, intermediate-term and long-term). The molecular induction and expression requirements of these forms of memory will also be examined in this phase of the project. (2) A SYNAPTIC ANALYSIS will be aimed at exploring, at a synaptic level, the different forms of memory revealed in behavioral studies, examining whether synaptic correlates of memory can be identified in the CNS, and whether behavioral memory can be blocked or enhanced by direct manipulations in the CNS. (3) A MOLECULAR ANALYSIS will be aimed at examining molecular correlates of different phases of memory, and establishing direct links between the induction of specific signaling cascades and activation of specific genes, and the induction of specific phases of memory. The importance of memory can perhaps be best appreciated by considering the devastating consequences of memory systems gone awry, such as the case in Alzheimer's Disease, Post-Traumatic Stress Disorder and victims of stoke or accidents that impair brain function. Thus understanding brain processes involved in memory formation is of fundamental importance both from a basic scientific perspective, with the goal of providing mechanistic insights into a fundamental aspect of cognitive behavior, and from a clinical perspective, with the goal of providing the basis for effective therapies for cognitive problems involving memory impairment.